Production of aviation or motor fuels



Dec. 12, 195o D. A. HowI-:s ETAL PRODUCTION OF AVIATION Oa MOIOR FUELSFiled Dec.

lvnm' Pond/a fber Howes Thomas 7.6/2"

'y 5 dtg'neys EQ WEWQQQQ Patented Dec. 12, 19950 UNITED `STATES BFENT yOFFCE PRODUCTION OF AVIATION OR'MOTOR.

FUELS 4 Donald A. Howes and Thomas Tait, Sunbury-on- Thames, England,assignors t Anglo-Iranian Oil Company Limited, London, England, aBritish joint-stock corporation Application December 15, 1948, SerialN0. 65,468

In Great Britain May 5, 19541 l i0 claims. (o1. 19e-7s) o The inventionrelates to the production of high ade aviation or motor fuels or motorfuel coni ituents. More particularlythe invention relates to theproduction of high grade motor fuel fromAv ieedstocks containingappreciable proportions of tillates that appreciable quantities ofstable high grade aviaion spirit may be obtained from them. Theinvention is not limited to any particular nod oiproducing thefeedstock. The cracked dist ate subjected to the process of theinvention may for example'be obtained from a crude stock and compriseany fraction derived from a crude mineral oil ranging from naphtha toheavy residuum. Particularly good results are obtained however in theuse as feedstocks of cracked distillates obtained in thermal reformingoperations,

in which the feedstocks are those generally known asnaphthas having aboiling range approxiniating '70 C.-300 C. The thermalreformingconditions usually vemployed in such cases varyas'to'temperature between 480 C. and 700 C. and as to pressure between100 and 2,000 lbs.'

per square inch. The condensible gases formed in the process, being Caand Ci hydrocarbons may be recycled to thecracking still and mixed withthe naptha feed. In generalthe cracked distillate so produced will havean octane number (C. F. R. Motor Method) of from 65 to as high as 90 oreven higher, according to the character or composition of the napthaprocessed and the reforming conditions employed. In the nature of thecase products of higher octane number re- V'quire the use of moredrastic conditions of reforming in the use of higher temperatures in theranges.

According to the invention a feedstock containing mono-olenes and/ordi-olefines, such as the cracked distillates referred to, is submittedto hydrogenation to convert the mono-olefines and/or di-olefines intothe corresponding paraiiin or naphthene hydrocarbons, and the treatedmaterial including the saturated products Yare thereupon fractionatedfor the separation of hydrocarbons or fractions of low` octane memberconsisting mainly of the normal parains and simple branched* chainparaffins of low octane number, and for the recovery of hydrocarbons orfractions of. high octane` number consisting mainly` of lyst per hour.

naphthene hydrocarbons and branched 'chain'. paraffin hydrocarbons ofhigh octane number;` under the conditions hereinafter more particular-57ly described;`and the hydrocarbons or fractions" of high octane numberrecovered may be blend-A ed together, and with hydrocarbons suchua's:toluene, Xylene-and higher aromatic hydrocar-jv bons recovered in knownmanner as by solvent extraction `from the recovered hydrogenated'product or a fraction thereof. The high octane number hydrocarbons orfractions may be used` individually or together in Varying proportionsas constituents of a high grade motor or aviation' fuel. i f

The` feedstock may be first desulphurized or may be desulphurized underthe conditions of hydro:l genation. The preliminary desulphurization 'ishoweveronly. necessary if the feedstock contains -3 proportion ofsulphur compounds injurious to hydrogenation catalyst employed.

'The invention comprises the. process` conditions.

hereinafter. described.

ln carrying the invention into effect the hydrogenation treatment may becarried 4out .on a. cracked distillate having for example a finalboiling point of 200 C. to 300'C. at a temperature within the range 'C.to 300 C. and at agspac'ef velocity of 0.5 to 5.0 volumes per volume ofcata: Hydrogen is advantageously einployed in excess, and thehydrogenating catalyst may conveniently consist of or contain a mixtureof tungsten and nickel sulphides, or cobalt molybdate or nickelmolybdate or reduced iron oxide or a mixture of alumina and nickeloxide;The hydrogenated product may ordinarily contain a small quantity ofhydrogen sulphide' in solution, which may be removed by washing' thehydrogenated product with an alkaline solution such as a solution ofcaustic soda. The Vmonoolenes and/or d-.olenes of the feedstock 'areconvertedunder the conditions of treatmentinto' the correspondingparaffin and naphthene hydro'i earbons by simple addition ofhydrogen.unaci coinpanied by any substantial formation 'ofhyI drocarbonsof lower molecular Weight. l j

Where the feedstock has a sulphur content injurious to the catalyst thatmay be employed for its hydogenation, `the feedstock may be drstsubjected to treatment for. thesubstantial removal of the sulphurcompounds. Hydrogenation 'cata-1 lysts are aifected'in a varying degreeby the presi ence of sulphur'compounds. Thus simple reduced nickelcatalysts are rapidly poisoned by very small amounts of sulphurcompounds,A for example` 0.01% or less, while mixtures of tungsten *andVat a temperature within the range '530' C. to

'700 C., and at a throughput of" from 0.5 `to I0. liquid volumes pervolume of catalyst per hour, in the absence of hydrogen.-llllternativelyfdesul'` -fphurizing catalysts comprising mixtures ofmolybdic oxide and alumina, or chromic oxide andv lalumina may beemployedunder the same re-V action conditions, but in the. presence ofadded hydrogen., In this` manner the sulphur content of the, crackeddistillate may be reduced from for example 0.1% to less than 0.001%'.

The hydrogenated product may then be fractionated under conditions ofprecision in fractionation determined to insure control of top andbottom temperatures, reflux.` ratios` and pressures inthe fractionatingcolumns and vin thev use of the. equivalent of' 50 or more theoreticalplates,

whereby thev normal paraffin hydrocarbons or fractions rich in suchconstituents are removed. SuchV normal,` hydrocarbons. present in thefeed'- stock or Vformed during the treatment that results in the simplesaturationof straight chain olene hydrocarbons, are of. low` octanenumber,

as indicated by the following gures:

Octane number (C. EUR.. Motor) Normal pentarre.. .'c 61 Normal hexane 25Normal heptane Normal octane 17 Normal nomme 45 Their removal thusresults inamarked increase A' in thei octane number of, suchhydrocarbons or fractionsrecovered;

'The hydrogenated product may be fractionated to form a lighter andaheavier' fraction and that part. ofthe hydrogenated! product, boilingabove about` 100 C. may be treated with a selective solventv for Vtherecovery ofaromatic hydrocarbons. such as toluene, xylene, ethylrbenzene and higher aromatic hydrocarbons. For Vthis purpose liquidsulphur dioxideY may advantageously be. used and the treatment carriedout in known manner at a low temperature of'from 10"0. to -80 C.,whereby theY aromatic hydrocarbons are recoveredA in a highconcentration.V The lighter fraction may be fractionated Vunder thecondimay. have been recovered from that. part of the hydrogenatedproduct boiling up to 100 C. and

from which the normal parallins or fractions rich 4 in normal parainshave been removed in the manner under the conditions described.Y

The invention is diagrammatically illustrated by way of example in theaccompanying drawing.

In carrying the invention into effect as illusV trated in theaccompanying drawing a feedstock, such, for example, as a distillateproduced in the thermal cracking or thermal reforming operation isdesul-phurized under known conditions such as hereinbefore described ina preliminary treatment stage 7c if it contains an appreciableproportion of sulphur, and is thereupon hydrogenated in a known mannerin asucceeding stage l under conditions such as hereinbefore describedfor the conversion of the mono-olene and di-clene content, intocorresponding paraffin and naphchene-hydrocarbons.

The hydrogenated product is then fractionated in a fractionator L toobtain a light fraction as an overhead product and a heavier fraction asa Y bottoms product. Y

The bottoms product of the fractionator- L,

which may advantageously be that part of the hydrogenated productboiling above C., is passed for solventextraction or its aromatichydrocarbon content through the solvent extraction andfseparating plantm, which operates in known manner, the materialv flowing successivelylirst into a mixingtank in which itis contacted with liquid sulphurvdioxide under known conditions, whereuponA the mixture passes into asettling tankfor'the settlement andI separation of the extract andralnnate phases; The aromatic extract thence passes asreed to a' columnfor the removal of the liquid sulphur dioxideasoverhead and the aromaticextract as bottoms, which latter may.' pass to storage for'eventual useof the material asa fuel blending constituent inthe proportions'thatmaybe stipulated-byfuel specifications, while the railinate passes asfeed to a column Where the sulphur Vdioxide is separated and theralhnate passes' to storage.

' The overhead: product. of the'fractionator L is passedto the first ofa series offractionating col'- umns. a, IJ, c', d' ande for theseparation under conditions of` precision in fractionation of0 hydrocarbons or fractions consisting mainly or they normal paramos VandVsimple branched chain parafns oil low'octane numbenan'difortherecoveryof Vhydrocarbons or fractions of high octane number consistingmainly ofV naphthene hydrocarbons and branched `chain paraihnhydrocarbons of high octane number. Y

Each ci the columns is vprovided for example withY the equivalentiofamoderately large number of theoretical plates not substantially lessthan 50 theoretical plates and a moderate redux ratio maintained inoperation 'of the columns for example of. 15 1,V and'` top and bottomtemperatures maintained in the. columns under control by analysis andthe use oilaboratory equipment and a moderate pressure applied in thecolumn in which isopentane is recovered,'whereby the operatingconditions may be precisely controlled in the respective columns havingregard to the determinations thus madeV as to composition.V

The temperature conditions are determined in the columns such that anisopentane fraction is recovered in the column a as overhead from normalpentane and higher hydrocarbons which leave as bottoms. The latterthence passes into the column b ata mid-position in its length where theoperating conditions are so determined that normalpentane is4 separated`as overhead and higher hydrocarbons' leave as bottoms. The latter' thenpasses to a mid-position in the column' c in which an iso-hexanefraction is recovered as overhead having an approximate boiling range of45-64 C. including cyclopentane and the'four hexane isomers to thesubstantial exclusion of normal hexane which leaves thev columnA c withthe higher hydrocarbons as bottoms, to enter. the next column d at amid-position, where the. normal hexane fraction is separated as overheadand the remainder as bottoms. The latter then passes in a mid-positionto the column e, where at a moderate redux ratio of approximately :1 arecoveryof ran isoheptane fraction is made as overhead, having theapproximate boiling range of 72-92 C. comprising the content of cyclichydrocarbons and branched chain hydrocarbons boiling in that range tothe exclusion of any substantial proportion of 2-methyl hexane, S-methylhexane; S-ethyl pentane and normal heptane which leaves the lcolumn ethrough the pipe 3 together with the hydrocarbons boiling beyond thatrange. s

The high grade overhead fractions from the columns a, c and e pass bythe respective lines ai, c1 and e1 to the respective storage vessels a2,c2, and e2 whence they may be withdrawn as blending constituents for usewith the aromatic extract hereinbefore described in the proportions thatmay be stipulated by fuel specifications.

The normal pentane and normal hexane fractions leaving as overheadrespectively from the columns b and d may pass by the pipe line b1 tostorage.

It will be understood that the extentof fractionation will depend uponthe initial boiling point of' the feedstock. Thus according to itscomposition, the feedstock may only require frac- -tionationin thecolumns b, c, d and e or other smaller number of columns according toits content of normal parafn hydrocarbons and of its content ofisopentane and of the isohexane and iso-heptane fractions.

This application is a continuation-in-part of our copending application,Serial Number 444,260, filed May 23, 1942, and now abandoned, forImprovernents relating to the production of aviation or motor fuels.

What is claimed is:

1. A process for the production of blending constituents of an aviationor motor fuel of high octane number from a substantially sulphur-freecracked petroleum distillate containing monoolefines and di-oleflnes,comprising subjecting the sulphur-free feedstock to hydrogenation forthe conversion of the mono-olefine and di-oleflne con- L tent intocorresponding paraflin and naphthene hydrocarbons by simple addition ofhydrogen, separating the hydrogenated cracked distillate into a lighterfraction boiling up to about 100 C. and into a heavierfraction,'subjecting said lighter fraction of the hydrogenated crackeddistillate to fractionation for the separation therefrom of at least onenormal fraction, namely normal heptane together with the content of saidlighter fraction boiling beyond about 92 C. and for the recovery fromsaid lighter fraction of at least one fraction of high octane number,namely a fraction having an approximate boiling range of about 72 C`. toabout 92 C. comprising the content of cyclic hydrocarbons and branchedchain hydrocarbons boiling in that range to the exclusion of anysubstantial proportion o-f 2-methyl hexane, S-methyl hexane, 3-ethy1pentane and normal heptane, the fractionations being carried out underconditions of precision in the main tenance of determined top and bottomtempera-7 tures and pressure, in theV use of columns having theequivalent of a moderately large` number of theoretical plates notsubstantially less than 50 theoretical plates, and a high reflux ratio,in gen.- eral not substantially less than 15:1, and subjecting the saidheavier fraction of the hydrogenated cracked distillate boiling beyondabout C. to solvent extraction for the recovery from said heavierfraction of an aromatic hydrocarbon extract as an additional blendingconstituent.

2. A process as specified in claim 1, in which the material fed to thecolumns is analyzed. and the operating conditions precisely controlledin the columns having regard to the determinations made. A

3. A process for the production of blending constituents of an aviationor motor fuel of high octane number from a cracked petroleum distillateas specified in claim 1, in which the said lighter fraction of thehydrogenated ycracked distillate before being fractionated for theseparation of normal heptane, is fractionated under the same conditionsof precision in fractionation for the recovery of a fraction of highoctane number having approximately a boiling range of 45-64 C.comprising substantially the content in the hydrogenated crackeddistillate, of cyclopentane together with the dimethyl butanes and themethyl pentanes boilingin that range as an 'additional blendingconstituent.

4. A process for the production of blending constituents of `an aviationor motor fuel of high octane number from a cracked petroleum .distillateas specified in claim 1, in which said lighter fraction of thehydrogenated cracked distillate before being fractionated for theseparation of normal heptane, is fractionated under the same conditionsof precision in fractionation for the recovery of a fraction of highoctane number having approximately a boiling range of 45-64 C.comprising substantially the content in the hydrogenated crackeddistillate, or cyclopentane together With the dimethyl butanes and themethyl pentanes boiling in that range as an additional blendingconstituent and in which theI material fed to the columns is analyzed,and the operating conditions precisely controlled in the columns havingregard to the determinations made.

5. A process for the production of blending constituents of an aviationor motor fuel of high octane number from a cracked petroleum distillateas specified in claim 1, in which the said lighter fraction of thehydrogenated cracked distillate before being fractionated for theseparation of normal heptane is fractionated under the same conditionsof precision in fractionation for the separation of normal pentane, forthe recovery of an additional fraction of high octane number havingapproximately a boiling range of 45-64 C., comprising substantiallyl thecontent in the distillate of cyclopentane together with the di-methylbutanes and the methyl pentanes boiling in that range, as a blendingconstituent, and for the recovery of the content of isopentane, as ablending constituent.

6. A process for the production of' blending constituents of an aviationor motor fuel of high octane number from a cracked petroleum distillateas specified in claim 1, in which said lighter fraction of thehydrogenated cracked distillate before being fractionated for theseparation of normal heptane is fractionated under the same conditionsof precision in fractionation, for the separation of normal pentane andnormal :fhexa'ne,' for the recovery vof a zfraction of high -octanenumber :having approximately Vla boilinef"Y range of l5i-64 iC..comprising substanf tially ithe content in ithe distillate of :cyclopenetane Itoge'ther with vthe diemethy'l :bu'tanes :and the methyl `pentanes`boiling 'inthatqranges as :a `blending constituent, and fior thelrecoveryvof thescontent 'of isopentanegas a 'iblendinga constituent,andl in which the. material fed `tothe column is ianalyzed, and `the:operating .zconditions'ypr ciselycontroiled in lthe Acolurmzrshavingregardito the 'determinations made.` i

'7.'.1.,p'1-ocess A'for the production -of blending constituents of fanavation or motor :fuel of :high cctanenumber from a cracked:andhydrogenated distillate asspeciledA in claim 1, in which theV:fraction having 'fa boilingfrange of v72" tofabout v922C.is recoveredina `-column operatingi'atla reflux ratio of substantially 110:1.

28. A A*process for the production-:of `blending l `constituents l ofkan laviation or motor fuel -as speciedin claim il, in'whichthescrackeddisr- `tillatelo'as Ya nal boilingpoint of from 20'0"'C.

"to 300 C.:and is hydrogenated'atxa temperature yinthe lrange150'C.-'300"'C.and Iatfzaxspace vei; t

klo'city `.of 10.5 yto j5'.0"vo1s. per' vol. of catalystV per hour.

'9. A Aprocess .for the :production `Vof :blending i'constituents of ianaviation or :motor fuel Yas speciied.y in :claim "1, Ain IWhichthe:cracked 'feedstock is hydrogenated in the presence of: hydro- 210, fAprocess Lior l.the1preduction of .blending Vconstituents Vof an aviationor :zmotor fuel of "high octane number fromY 'asnbstantially sub iphu'r-'free cracked Avpetroleurn `distillate containingmono-olenes vvanddiolenes comprisingr the hydrocarbons `by simple '.:additio'n :oflrlylnig'ens:- subjecting :the y,lighter z'portion -of :the`Vihydroggenated .product .boiling up :to 4about ,110,0" IC. to'fractionation for :the 5*separation itherefrom of "at least one normaliraction, namely normal hep-f .tane :together with ithe .content .ofsaid jlighter portion boiling 1 beyond z about 92 `C. .and for therecovery from said lighter portion `of -at least one -fraction ofzl'xighxoctaneinumber, namely a fraction having an Aapproximate thoiling,range Ycontent `of --cyclic hydrocarbons .and branchedfchainhydrocarbons' boi1ing; in thatrange ato the "exclusion-of anyysubstantial proportion of "2,- Y'methyl hexane, -methyl hexane, 3-ethylapen Etane and lnormal heptane, the fractionation 1be ing carried foutunder conditions. of precision` in -the maintenance of `determined topand bottom temperaturesand pressure, inthe .use'of columns having vthe:equivalent of Vfa moderately --large number of theoretical plates vnot-substantiail'y less than 50 theoretical plates, and a highi'eiluxAVratio, in general 'notsubstantiallyj lessV than F15 l.

"DONALD A. HOWES. THOMAS-TAH.

REFERENCES curan i Th'ejfollowlne references `areo record `ins-the illeof this patent:

Y UNITEDfsTATEsPATENTS vNumber 'rfName Date 2,055,455 Taylor et a1.Sept. '22,1936

OTHER REFERENCES l? Petroleum Processing, vol. 2,.;No. 21.(Feb., 19471,

vpages 1:36, Y139,.*'14o142,143, .145 and 146 article "by 'lf-Birch,Doeksen fand Dove V'on ,Supe'rfrace nonanonn. -V

10. A PROCESS FOR THE PRODUCTION OF BLENDING CONSTITUENTS OF AN AVIATIONOR MOTOR FUEL OF HIGH OCTANE NUMER FROM A SUBSTANTIALLY SULPHUR-FREECRACKED PETROLEUM DISTILLATE CONTAINING MONO-OLEFINES AND DIOLEFINESCOMPRISING THE STEPS OF HYDROGENATING THE FEEDSTOCK FOR THE CONVERSIONOF THE MONO-OLEFINE AND DIOLEFINE CONTENT INTO CORRESPONDING PARAFFINAND NAPHTHENE HYDROCARBONS BY SIMPLE ADDITION OF HYDROGEN; SUBJECTINGTHE LIGHTER PORTION OF THE HYDROGENATED PRODUCT BOILING UP TO ABOUT100*C TO FRACTIONATION FOR THE SEPARATION THEREFROM OF AT LEAST ONENORMAL FRACTION, NAMELY NORMAL HEPTANE TOGETHER WITH THE CONTENT OF SAIDLIGHTER PORTION BOILING BEYOND ABOUT 92*C AND FOR THE RECOVERY FROM SAIDLIGHTER PORTION OF AT LEAST ONE FRACTION OF HIGH OCTANE NUMBER, NAMELY AFRACTION HAVING AN APPROXIMATELY BOILING RANGE OF ABOUT 72*C TO ABOUT92*C COMPRISING THE CONTENT OF CYCLIC HYDROCARBONS AND BRANCHED CHAINHYDROCARBONS BOILING IN THAT RANGE TO THE EXCLUSION OF ANY SUBSTANTIALPROPORTION OF 2METHYL HEXANE, 3-METHYL HEXANE, 3-ETHYL PENTANE ANDNORMAL HEPTANE, THE FRACTIONATION BEING CARRIED OUT UNDER CONDITIONS OFPRECISION IN THE MAINTENANCE OF DETERMINED TOP AND BOTTOM TEMPERATURESAND PRESSURE, IN TEH USE OF COLUMNS HAVING HE EQUIVALENT OF A MODERATELYLARGE NUMBER OF THEORETICAL PLATES NOT SUBSTANTIALLY LESS THAN 50THEORETICAL PLATES, AND A HIGH REFLUX RATIO, IN GENERALY NOTSUBSTANTIALLY LESS THAN 15:1.